are in critical condition. several people required amputations and doctors say more arelikely.nbcnewsjusticecorrespondent pete williams is standing by. i am just reading information that you put in regarding the components of this bomb and what authorities believe was used to make the explosives. what can you tell me? >> they say they were crudely made. that doesn't mean that they weren't powerful and they were. they were made with gunpowder, bbs and ball bearings packed inside a pressure cooker. let me point to a picture from a homeland security bulletin. we're going to get in real tight on these little pots down here. this is what pressure cookers look like. give it a second to focus and see how much tighter we can get. these are what pressure cookers look like in case you haven't seen them. these are rather inexpensive pressure cookers. in case you've not ever dealt with one. a pot with a cover on it that you can make basically air tight and food cooks faster. and then for at least a decade, they've been used to make bombs around the world. so inside is the explosive and the authorities